There have been various attempts to provide a variable height surface on a ladder for the support of tools, parts, and other materials. Examples are "Ladder Lift With Swivel Tray" (U.S. Pat. No. 5,544,718), "Ladder Shelf" (U.S. Pat. No. 5,120,013), and "Ladder Aid Device" (U.S. Pat. No. 4,418,793), all of which are hereby incorporated herein by reference.
The devices of the aforesaid patents have numerous problems and fail to provide important features that certain embodiments of the instant invention incorporate, such as: central location relative to the ladder assembly, simplicity, versatility, light weight, portability, ease of adjustment, and/or storability within the confines of the ladder.
In U.S. Pat. No. 5,544,718, the swivel tray assembly does not provide stability because as it is raised, the load is shifted further and further off center in many locations of the tray. This is potentially dangerous. The device is not versatile in that it has limited use and limited adjustment. The device further incorporates two sizeable steel shafts and tubes which add considerable weight to the ladder. Because the device is mounted to the outside of the ladder it will interfere with the transportation and storage of the assembly, and potentially with a user climbing up the ladder.
In U.S. Pat. No. 5,120,013, the assembly is mounted entirely on the rear legs of the ladder, making it potentially unstable. This of course is dangerous, and could potentially interfere with a user climbing the ladder. The device is not versatile and would add considerable weight to the ladder. The device also cannot be adjusted while standing on the ladder and would be difficult to carry and store. Moreover, the material being supported by the shelf of the '013 patent would be located substantially off-center of the ladder thereby increasing the liklihood of ladder tipping.
In U.S. Pat. No. 4,418,793, the assembly is simple but has limited use. The device is mounted on one side edge of the ladder and is raised at an angle. The further it is raised the more unstable the assembly becomes, especially when material of considerable weight is on the shelf.
It is apparent from the above that there exists a need in the art for a variable level support for use with a stepladder or the like which is simple, can be used to provide a vertically adjustable support surface, does not substantially increase instability of the ladder, can support work material approximately near the center of the ladder so as to minimize the potential for ladder tipping, can be stored within the ladder, is versatile, can be used when both leg portions of the stepladder are extended opposite from one another, and/or can be used when only one leg portion of the ladder is being used to support the ladder (e.g. when the ladder is being leaned up against a wall or the like).